1. Field of the Invention
The present invention relates to a device for writing and reading data by using a cantilever, and more particularly, to a device for writing and reading data by using a cantilever, in which a resistively heated tip is used in writing data and a piezoelectric-sensor is used in reading data, for prevention of sensing error and reduction of a power consumption, and piezoelectric actuator array makes the height of cantilever array be uniform, for prevention of wear of a tip.
2. Background of the Related Art
In general, an Atomic Force Microscopy (AFM) measures a surface form and the like by using a micron cantilever. The cantilever has a tip of a few nm size at an end thereof, for measuring an atomic force between the tip and a specimen for detecting the surface form or electric or magnetic properties of the specimen.
Recently, research on nano-lithography devices or nano data storages of the atomic force microscopy principle has been active. The atomic force microscopy principle enables storage of data using a probe of a few nm in size, to develop a data storage having a storage density higher than a tera bit/in2. IBM of the USA has studied a data storage device of a polymer recording medium of the atomic force microscopy principle for a few years.
FIG. 1 illustrates a perspective view showing a state in which a related art atomic force microscopy writes data, schematically, wherein the IBM has designed the AFM data storage device provided with two dimensionally linked 32×32 unit cantilevers each inclusive of a silicon tip 10, a resistive heater platform 11 at the tip part, a unit cantilever having a cantilever part 12 connected to the resistive heater platform 11 and floated by a support 13.
In writing data by using the data storage device, the silicon tip is heated, to reduce a viscosity of the polymer recording medium 22 on a silicon substrate 21, a force is applied to the recording medium 22 locally by using the silicon tip 10, to form an data storage recess 23 in the recording medium 22. Thus, data is recorded.
On the other hand, referring to FIGS. 2A and 2B, in reading data by using the AFM data storage device, a principle is used, in which a heater cooling rate is varied with a distance between the heater platform and the recording medium.
In more detail, referring to FIG. 2A, if the silicon tip 10 is inserted into the data storage recess 23 in the recording medium 22, making a distance between the heater platform 11 and the recording medium 22 near, the heater platform 11 is cooled down quickly, and, referring to FIG. 2B, if the silicon tip is on a flat surface of the recording medium, with the distance between the heater platform 11 and the recording medium 22 far, the heater platform 11 is cooled down slowly.
Such a difference of cooling down rates varies a temperature of the heater platform 11, with a consequent variation of electric resistance, using which data is read.
Though the related art AFM data storage cantilever developed by the IBM has an advantage of simple fabrication process, it has the following problems.
First, the parallel cantilever array for faster AFM data storage is liable to cause failure in forming uniform heights of the cantilever tips due to deviations of layers of SOI substrates, and etching, which in turn causes deviations between the recording medium and the cantilever tips. The height deviation is greater than approx. 80 nm, significantly greater than a depth of the data storage recess of 40 nm, that deteriorates a reliability of the AFM data storage, and causes a serious wear down problem.
Second, the array of cantilevers require to have uniform heater platforms. If resistances of the heaters are not uniform, a reading reliability can not be secured.
Third, the heating of the heater platform to approx. 350° C. for detecting change of resistance of the heater platform and reading a data consumes much power, and, in the case of the array of the cantilevers, the power consumption is much higher as hundreds of heaters are heated at the same time. Since the nano data storage of the AFM principle is mostly for application to portable apparatuses, the high power consumption is a big disadvantage.